1. Field of the Invention
The present invention generally relates to an apparatus such as a camera, particularly relates to a camera employing a thrust-type of a cartridge, and more particularly relates to a mechanism, for locking a cover of a cartridge compartment of the camera, which prevents the cover from being opened when the camera is loaded with the cartridge, so that a film thereof is prevented from being exposed to light carelessly.
2. Description of the Related Arts
Conventionally, there have been provided various types of locking mechanisms for locking a cover of a film cartridge compartment in order to prevent the cover from unlocking carelessly, as shown in Japanese Laid-Open Patent (Unexamined) Publication Nos. 55-46732 and 54-128732.
According to the invention disclosed in the former Publication, the locking mechanism has a construction in which the spool for winding the film has a small diametric part and in which a lever is mounted in such a way that the lever is biased so that the small diametric part of the spool is pushed by the tip of the lever. With this construction, when the film is wound around the spool through the tip of the lever and the small diametric part of the spool, the lever tilts and the mechanism for opening and closing the cover is locked, moving with the lever.
On the other hand, according to the locking mechanism disclosed in the latter Publication, there is provided a sensor or the like, and the mechanism for opening and closing the cover is locked by employing a magnet or the like when the film is detected by the sensor.
The former locking mechanism, however, has a disadvantage that the cover may not be locked certainly, especially if the film does not have a uniform flexural strength, because as the film is wound around the spool, the film is pressed towards the outer surface of the small diametric part of the spool by the tip of the lever, thus letting the film bend. In addition, the former locking mechanism has another disadvantage that the film may get scratches on it or the frame set ready for picture taking is hard to get enough flatness because the film is pressed by the lever. On the other hand, because the latter locking mechanism employs an actuator like a magnet in exclusive use for it in order to lock the cover, such problems as a high cost of production and the camera becoming large-sized occur.
In a film cartridge of 135-type used conventionally, a leading end of the film is outside the film cartridge when the film is not used, and the leading end thereof is pulled out of the cartridge in winding the film around the cartridge spool.
This type of film cartridge has, however, such problems as it is not easy for a user to set the film cartridge inside the camera, and some load is necessarily exerted on the film during its movement because the film is prevented from being exposed to light by brush, sandwiching the film, mounted in the vicinity of the film entrance/exit of the film cartridge.
In order to secure the film cartridge in the cartridge compartment, the film cartridge is kept in the cartridge compartment with an outer wall of the film cartridge pressed against a wall of the cartridge compartment, as disclosed in Japanese Laid-Open Patent Publication No. 3-135536 and so on. That is, because the film is pressed by the inner wall of the outer shell of the film cartridge case, not only the film is hard to get enough flatness, but also a larger amount of driving force to feed the film is needed. In addition, unless the outer shell of the film cartridge is pressed firmly against the wall of the cartridge compartment, a rotational center of the cartridge spool may become out of position with respect to the camera body while the film is fed. At this moment, a load in feeding film may increase due to a drift or deviation of the film with respect to the position of the entrance/exit of the film cartridge in the vertical direction. Furthermore, if it happens that the position of the cartridge spool itself changes, the load in feeding film may also increase due to a frictional change in rotation. In order to solve this problem, a thrust-type of cartridge as disclosed in Japanese Laid-Open Patent Publication No. 2-181141 and a camera as disclosed in Japanese Laid-Open Patent Publication No. 4-1621 employing this type of cartridge have been proposed.
The thrust-type of cartridge is constructed so that the film thereof is wound up to the tip of the leader inside the film case when the cartridge is not set inside a camera and that the film is thrust and fed out of the film cartridge by a mechanism, for feeding the film, provided on the side of the camera when the cartridge is set inside the camera, and the film fed therefrom is wound around the spool of the camera. If the camera is of the type in use for the thrust-type of cartridge, it is possible to make the cartridge compartment cover relatively smaller and to provide this on either the upper or lower surface of the camera body because of being able to put the cartridge in and out the cartridge compartment in an axial direction of the spool. In case of using this type of camera, if the user opens the cartridge compartment cover and tries to take the film cartridge out of the cartridge compartment by force when the film is fed out of the cartridge, not only the film is exposed to light, but also there may arise such a possibility as the film tears and any torn pieces of the film remain inside the camera. If this happens, since the cartridge compartment cover is small, it is difficult for the user to remove the remains of film from the cartridge compartment, and it may be necessary to repair the camera.
Furthermore, as shown in Japanese Laid-Open (Unexamined) Patent Publication No. 3-267933, there has been proposed a cartridge, of the same thrust-type of cartridge, being constructed so that a member having an index or an indicator on it is integrally mounted to the cartridge spool and rotates together with it, that marks of "EXPOSED", "UNEXPOSED" or the like to display how the film is used are shown on the cartridge case, and that the indicator points to either of these displaying marks, depending upon the state thereof, by controlling the stopping position of the cartridge spool at the time of rewinding the film. In case of using this type of cartridge, if the cartridge is taken out of the camera before the positioning of the indicator with respect to a predetermined displaying mark is completed, the indicator points to a wrong display mark. In order to prevent this wrong indication of mark, it is preferable to prevent the cartridge compartment cover from being opened unnecessarily.
Meanwhile, a film cartridge as disclosed in Japanese Laid-Open Patent Publication Nos. 63-305350 and 1-191837 has a light-intercepting member or door, which can be opened and closed, provided in the film entrance/exit. In a type of camera employing this type of film cartridge having the light-intercepting door is provided a mechanism by which the door is opened before feeding the film after the film cartridge is set inside the cartridge compartment and by which the door is closed before taking the cartridge out of the compartment after the rewinding of the film is completed. With this construction, however, there is a possibility that the light-intercepting door thereof may open before the cartridge compartment cover is completely closed, and if this happens, the film is exposed to light carelessly. For example, the light-intercepting door disclosed in the Publication No. 63-305350 is pivotally mounted in the cassette case, and the door is biased in such a direction that the film exit is closed. In the cassette case, a side wall of the film entrance/exit has a hole formed therein, and a pin for pressing the door is slidably mounted in the hole so as not to be dropped off so that the pin presses the door to open, the film entrance/exit. On the other hand, in an opening and closing door of the camera is formed a projection to press and move the pin into the cassette case. Namely, when the pin is pushed in the cassette case by the projection of the opening and closing door, the light-intercepting door is opened. The light-intercepting door starts to open when the projection of the opening and closing door starts to press the pin; therefore, if the light-intercepting door starts to open before the opening and closing door is completely closed, the film may be exposed to light carelessly. That is, because the mechanism to open and close the light-intercepting door operates after the camera is loaded with the film cartridge and before the cartridge is taken out of the camera, the mechanism to open and close the door can be constructed so that it works with the locking and unlocking of the cartridge compartment cover through a linkage. However, in case that the linkage is provided in a camera, it is difficult to make a camera small-sized, because the mechanism to open and close the light-intercepting door is, generally, disposed opposite the mechanism to lock the cartridge compartment cover of the camera.